Gibbous Moon

A few nights ago I noticed a white spot on the terminator of the gibbous Moon (just above the middle of the left-hand edge).  I have noticed this before many times, and have always assumed that it was the bright patch around the crater Copernicus.  However, this time I decided to check this by taking a photo (hand-held, through an open window) and this was the result.  What it shows is that the white spot is not the area around Copernicus but the brightly sunlit inner wall of the crater.  I should really have known this, as the area around the crater only becomes bright when the sun is overhead.

Photo taken on 2010-10-17.